Ferromagnetic spin alignment in head-to-tail coupled oligo(1, 4-phenyleneethynylene)s and Oligo(1,4-phenylenevinylene)s bearing pendant p-phenylenediamine radical cations

The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical cations in head-to-tail coupled oligo(1, 4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that the radical cations are localized in the pendant p-phenylenediamine units of the conjugated oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1, 4-phenylenvinylene) di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the doubly integrated ESR intensity of the DeltaM(s) = +/-1 and DeltaM(s) = +/-2 signals with the inverse temperature (I approximately 1/T), consistent with Curie's law. This behavior indicates a triplet ground-state diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet states.     

Aminopropylcellulose,synthesis and derivatization

The preparation of 3-aminopropylcellulose from cyanoethylcellulose is readily achieved. Reduction of the cyano groups with borane-dimethyl sulfide in tetrahydrofuran or a borane-tetrahy-drofuran complex proceeds quantitatively in 3 h to a corresponding 3-aminopropylcellulose. The presence of primary amine functions is confirmed by spectroscopy and a positive ninhydrin test; the concentration of amino substituents, as ascertained by titration, ranged from 1.2 to 6.4 meq/g. Because the derivatives are neither soluble nor excessively swollen in water, applications as ion-exchange resins or chromatographic supports can be envisioned. Treatment of 3-aminopropyl-cellulose with acetyl chloride, phenyl isocyanate, or p-toluenesulfonyl isocyanate produced 3-acetamido-, 3-(N′-phenyluredo)-, or 3-(N′-p-toluenesulfonyluredo)-N-propylcellulose. Alkylation with methyl chloride yielded a water-soluble quaternary ammonium salt.     

Yrast excitations in129Te

Using an 11.4MeV/u¹³⁶Xe beam of the UNILAC accelerator of GSI and a^natW target, A=184 isobars were produced and separated by using an on-line mass separator. A new isomeric state was found in¹⁸⁴Hf. This state decays with a half-life of 48(10) s and emits three -rays of 73, 482, and 555 keV as well as lower-lying cascade transitions. The hindrance of the 73 keV-E1 transition with K=8 is compared with those of other even-even hafnium isotopes. The half-life of¹⁸⁴Lu was estimated to be between 15 and 25s.     

Observations of the low Earth orbit radiation environment from Mir

Recent measurements of the high-energy charged particle environment with the Radiation Environment Monitor (REM) aboard the Russian Mir space station are presented. Ionizing dose rates in a silicon detector have been measured with two shieldings. The dose is mainly accumulated in two distinct areas, the South Atlantic Anomaly (SAA) and the region of closest approach to the magnetic poles. Whereas the radiation in the South Atlantic Anomaly varied little during 1995, large changes of the daily absorbed doses in the polar regions are observed. A comparison of REM doses with the NASA AP-8 and AE-8 radiation models revealed major differences. AP-8 tends to underestimate the average REM doses, whereas AE-8 overestimates REM doses, and rather describes the worst case.     

Supramolecular phthalocyanine dimers based on the secondary dialkylammonium cation/dibenzo-24-crown-8 recognition motif

[formula: see text] New unsymmetrically substituted DB24C8-phthalocyanines, which are able to form complexes with suitable dialkylammonium cations, have been prepared. These complexes most probably have a pseudorotaxane geometry.     

High-performance liquid chromatographic assay for mitoxantrone in plasma using electrochemical detection

A sensitive and specific high-performance liquid chromatographic (HPLC) assay was developed for the quantitation of mitoxantrone in plasma using electrochemical detection. Bisantrene was chosen as the internal standard. A reversed-phase, 10-microns muBondapak C18 analytical column (30 cm X 3.9 mm) with an isocratic mobile phase of 28% acetonitrile in 80 mM sodium formate buffer (pH 3.0) was used. The eluent was monitored by both electrochemical detection at an applied potential of +0.75 V vs. Ag/AgCl and visible absorbance at 660 nm. Only electrochemical detection was able to quantitate the internal standard and provided ten times higher sensitivity than visible absorbance for mitoxantrone with a detection limit as low as 0.1 ng/ml. Calibration curves in the range 0.1-1000 ng/ml showed good linearity (r = 0.998) and precision (coefficient of variation less than 10%). This HPLC method utilized a reproducible and inexpensive liquid-liquid extraction procedure. Using methylene chloride, the extraction efficacy of mitoxantrone from plasma was 85.3% with a coefficient of variation less than 2.1%. This new assay was then applied to measure mitoxantrone concentrations in plasma obtained from two leukemic patients receiving 12 mg/m2 mitoxantrone as a 1-h infusion.